Constant pressure variable displacement pump



May 18, 1954 a. H. HUFFERD ETAL 2,678,607

CONSTANT PRESSURE VARIABLE DISPLACEMENT PUMP Filed April 2, 1948 6 Sheets-Sheet 1 IIIIIL l I I I lll llxllk frz VET? [0P5 6 6 02 96 H .Hzzffird & flew/Zara? E 0 'Connon f &M I H27 :5

May 18, 1954 e. H. HUFFERD ETAL 2,678,607

CONSTANT PRESSURE VARIABLE DISPLACEMENT PUMP Filed April 2, 1948 6 Sheets-Sheet 2 fnz E T02 5 61902 96 1? Hzzfferd 41 Bernard O'Con'rzor y 1-954 G. H. HUFFERD ETAL. 2,678,607

- CONSTANT PRESSURE VARIABLE DISPLACEMENT PUMP Filed April 2, 1948 6 Sheets-Sheet 4 271 5172 0P5 Geo/:96 .H Hzzfierd 41 Bernard E 0 'Cozzrzor y 4 s. H. HUFFERD EIAL 2,678,607

CONSTANT PRESSURE VARIABLE DISPLACEMENT PUMP Filed April 2, 1948 6 Sheets-Sheet 5 Patented May 18, 1954 CONSTANT PRESSURE VARIABLE DISPLACEMENT PUMP George H. Hufferd, Cleveland, Ohio, and Bernard E. OConnor, Bufialo, N. Y., assignors to Houdaille-Hershey Corporation, Detroit, Mich, a

corporation of Michigan Application April 2, 1948, Serial No. 18,558

13 Claims. (01. 103-120) The present invention relates to improvements in constant pressure variable displacement pumps and more particularly to pumps of this character which are automatically adjustable in response to operating conditions and requirements encountered during performance of the pump.

Numerous attempts have heretofore been made to supply rotary, vane type variable displacement pumps having mechanical or more or less automatic control. However, the prior devices have inherently lacked or have been deficient in various characteristics which would render them satisfactory under as great a range of operating requirements and conditions as desirable. For example, certain constructions lack stability in that they will vibrate or chatter under certain operating conditions. They may be sluggish in operation so that undue back pressure develops before a change in displacement occurs. Changes in displacement may be accompanied by too great a pressure drop. Some are badly afiected by variations in temperature. Foaming of the hydraulic fluid frequently detrimentally affects operation of the pumps. Some constructions have lacked adequate ruggedness for operation under high pressures. Speed ranges for certain forms of the pumps have been seriously restricted.

An important object of the present invention is to provide a constant pressure variable displacement pump construction which satisfactorily overcomes the limitations and deficiencies of prior pumps of this character as enumerated hereinbefore, and to improve this kind of pump in various respects.

Another object of the invention is to improve constant pressure variable displacement pumps to attain great stability and freedom from vibration or chatter.

A further object of the invention is to provide improvements in pumps of the character referred to wherein the available fluid at high speeds remains substantially constant so that the pressure and volume remain at a desired value.

Still another object of the invention is to provide constant pressure variable displacement pumps of improved construction wherein a wide range of temperature conditions are adapted to be accommodated satisfactorily.

Yet another object of the invention is to provide improved constant pressure variable displacement pump construction which will operate efficiently. in spite of foaming of the hydraulic fluid.

A still further object of the invention is to provide constant pressure variable displacement pump structure of relatively simple, compact. rugged. and essentially trouble-free character.

Yet a further object of the invention is to provide improved displacement varying control means for rotary vanetype pumps.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of certain preferred embodiments thereof taken in conjunction with the accompanying six sheets of drawings in which:

Figure 1 is an elevational view of one face of a pump unit embodying features of the invention;

Figure 2 is an end elevational view of the pump unit;

Figure 3 is a sectional elevational view through the pump unit, taken substantially on line III-III of Figure 2 and on an enlarged scale.

Figure 4 is a sectional elevational view through the pump unit taken substantially on the line IV--IV of Figure 2, and on a substantially enlarged scale, with certain portions broken away for clarity of illustration.

Figure 5 is a sectional viewthrough the pump unit taken substantially on the line VV of Figure 3;

Figure 6 is a sectional elevational view taken substantially on the line VIV1 of Figure 4 and on a reduced scale;

Figure '7 is a fragmentary sectional elevational view of a slight modification in one portion of the pump unit;

Figure 8 is a diagrammatic view showing the hydraulic control circuit for the pump unit of Figure 1;

Figure 9 is a sectional elevational view through a modified form of pump unit, with certain parts broken away for purpose of illustration and taken substantially on the line IX-IX of Figure 10;

Figure 10 is a sectional view taken substantially on the line X-X of Figure 9;

Figure 11 is a diagrammatic view showing a modified displacement control arrangement which is applicable to either of the forms of Figure 1 or 9;

Figure 12 is a fragmentary diagrammatic, sectional elevational view showing the control valve of the form of Figure 11 in a different operative position than in Figure 11; and

Figure 13 shows the control valve in still anther operative position.

A pump unit l5 embodying the principles of the present invention, and as shown in Figures 1 to 6, inclusive, is of the type wherein a shaft it drives a rotor ii, keyed or otherwise secured fixedly thereto and with which is associated a series of radially recipl'ocable fluid impelling vanes The rotor ii is of a known type havin radial slots is for the vanes 58, the inner ends of the slots bein formed with circular enlargements 20 for freedom of action, and the inner edges of the vanes being in engagement with identical control rings 2! located in appropriate end rccesses 22 in the rotor (Figures 4 and 6).

The shaft i6 is journaled in appropriate bearings 23 and 2t carried by respective opposite face plates 25 and 21, respectively, secured as by means of screws rate opposite sides of a hollowbody block; 29. For attaching the unit in place in association with apparatus with which the unit may be employed, the face plate 2? may be provided with apertured attachment ears 3%. The face plate 25 may be formed with an inlet boss 3| and an outlet boss 32.' These bosses are centrally bored and appropriately tapped to receive hydraulic fluid ducts and communicate with appropriate communication undercuts 33 and 34, respectively, in the inner face of the plate 25 (Figures 1 and According to the present invention are provided within the pump unit for maintaining nearly as practicable a constant pressure of the hydraulic fluid at the outlet 32, in spite of wide variation in speed of the shaft l6 and thereby of the rotor IT, as well as a wide range of fluid demand at the outlet 32 or fluctuations in the fluid supply at the inlet 3|. This is accomplished automatically responsive to internal fluid pressures. To this end, the body block 29 is formed internally with a preferably rectangular chamber 35 of substantially greater area than required for the pumping sweep of the pump vanes l8, and formed at opposite sides with bearing pads 31. Within the chamber 35 is reciprocably slidably disposed a generally rectangular modulator block 38 whi h is shorter by predetermined extent than the length of the chamber 35 and has bearing pads 39 at its opposite sides which are slidably in engaged relation with the bearing pads 31 of the body block within the chamber. A circular pump chamber 4!! in the modulator block accommodates the pump rotor l! and is of a diameter to have the outer edges of the rotor vanes I8 bear uniformly slidably against the pum chamber wall. The relation of the modulator block 38 is such to the shaft l6 and the chamber 35 in the body block 29 that when the modulator block is slidably Shifted fully to one end of the chamber 35, in the present instance to the upper end as viewed in Figure l, full concentricity of the pump chamber 49 with the rotor ll is attained. When the modulator block is shifted to the opposite extreme end of the chamber 31, maximum eccentricity of the pumping chamber &0 relative to the rotor I7 is attained. Thus, rectilinear shifting of the modulator block 33 is efiective to vary and control the displacement of the pump from zero to maximum Means are provided for utilizing the dynamic fluid pressure of the pump for not only holding the modulator 38 in functional adjustment but also for slidably adjusting the modulator in both of its opposite directions of pump displacement modifying movement. For this purpose, the high pressure side of the pump is placed in communication with both opposite ends of the body block.

chamber so that the high pressure can act upon the respective opposite ends of the modulator 38. A convenient device for this comprises a passageway duct ti (Figures 3 and 5) which may be in any preferred form for manufacturing and assembly convenience and is here formed as a groove in the inner face of a. distributor plate 42 coextensive with and clamped between the face plate 25 and the body block 29. The groove 4! is of a length to extend to the opposite extremities of the chamber 35 so as to be in constant communication with pressure areas or sub-chambers i3 and ill at the respective opposite ends of the modulator 38. 7

High pressure fluid communication between the pump chamber to and the outlet passag 32 through the distributor plate 12 is elfected by way of a preferably semi-circular or generally kidneyshaped discharge port d5 of such length and disposition as to afford resistance-free pressure communication with the high pressure sideof the pump chamber 4&3. As best seen in Figure 3, the high pressure communication duct groove ii cuts across the high pressure port 45 so thatequal pressure conductivity is attained for each opposite end portion of the duct t I.

Fluid inlet communication through the distributor plate 22 is attained through an inlet port 47 extending therethroughi This port is substantially the counterpart oi the discharge port but is in communication at the inside with the low pressure or inlet side of the pump chamber it and at the outside with the undercut inlet passage 33 leading from the inlet 3! in the side plate 25 of the pump unit.

The high pressure delivered by the pump through the duct or communication passageway ll to the opposite ends of the modulator 38 tends normally to maintain the modulator in what may be called dynamic pressure balance, holding the modulator firmly against any tendency to vibrate or chatter. This is implemented by having the pressure areas 43 and M at the opposite ends of the modulator block adequately isolated from the low pressure side of the pump by the large bearing areas between the fiat faces of the modulator block 38 and the opposing flat close sliolable bearing surfaces of the face plate 2'! and the distributor plate 52 between which the modulator block is closely confined in free slidable relation. The pressure areas 43 and 44, ofl course, are also isolated from one another by the large intervening bearing areas between the modulator block and. the opposing plates of the housing casing and by the close bearing relation of the bearing pads 3'1 and 39 at the sides of the modulator block.

In order to insure that the pressure areas 43 i and M will be at all times open to the high-pres sure fluid from the pump, respective spacers are provided between the opposing walls of the modu iator block 38 and the end walls of the chamber 35. These comprise in the present instance a spacer pad cs projecting from the modulator block toward the opposing chamber wall within the pressure area es and a spacer pad 49 projecting from the chamber wall within the pressure area a l for engagement by the opposing end of the modulator block. Herein the arrangement is such that engagement of the modulator block 33 with the spacer pad 43, as shown in Figures 3 and 4; occurs at the maximum eccentricity of the pump chamber at relative to the rotor I1, while engagement of the spacer pad as 'on the modulator block with the opposing chamberwall occurs at the point of concentricity of the pump chamber with the rotor.

At the start of operation of the pump l5, it is, of course, highly desirable that there be maximum displacement of hydraulic fluid by the rotor vanes it so as to develop the desired pressure as quickly as practicable. In order to assure this, priming means are provided for normally biasing the modulator block 38 to the position wherein the pump chamber 50 attains maximum eccentricity relative to the rotor ll. Herein such means comprises biasing spring structure in the form of a pair of similar coiled compression springs 50 seated in appropriate spring sockets 5! adjacent the opposite sides of the modulator block in the end face thereof which includes the spacer pad 33 and with the outer ends of the springs bearing against the opposing wall of the chamber 35 within the pressure area 43. The springs 59 acting upon the modulator block 38 assure that when the pump stops the modulator block will not remain in idling relation to the rotor ll, that is, with the pump chamber it concentric with the rotor l'i. Since the modulator block 38 is thus positively biased or primed toward eccentricity relative to the rotor I1, starting of the rotor for pumping always finds the pump chamber All) disposed for fluid displacement.

During operation of the pump, however, fluid pressure is the medium for controlling the position of the modulator block 38. To this end control means are provided which operate to render the pressure areas 43 and M automatically responsive to variations in pressure in the pumping system to relatively alter the pressure fluid volume in the pressure areas for shifting the modulator block 38 reciprocably, thereby maintaining a mean pressure output at the pump outlet. Herein such means comprise an arrangement for controlled, automatically selective communication between the low pressure side of the pump and the respective pressure areas 43 and 44 to bleed sufiicient pressure fluid therefrom to effect dynamic unbalance to the extent demanded to adjust the pump displacement for maintenance of the predetermined mean output pressure. Accordingly, a lead-or? branch 52 of the intake port i'i (Figures 3 and 5) communicates by way of a bore or orifice 53 through the contiguous face of the modulator block 38 with a transverse control valve chamber bore E l within the modulator lock. Communication between the pressure area 63 and. the control chamber 54 is adapted to be effected through a passage 55 extending longitudinally through the high pressure side portion of the modulator 38 and having a leg, 51 extending transversely of the modulator parallel to and spaced from. the control chamber 54 and which in turn has a port 53 opening into the control chamber (Figures 4, 5 and 6). Communication between the control chamber and the pressure area 44 is efiected through a port 59 that opens through the end of the modulator 38. In the fully eccentric condition of the modulator 3B, the port 58 is bl sired by a lateral extension 490: of the spacer pad 39. It may be observed that the ports 58 and 55 are relatively ofiset considered 1ongitudinally of the control chamber 54 and enter the chamber approximately 90 apart.

For controlling communication of the low pressure port or orifice 553 with either of the ports '53 or 59 leading to the respective pressure areas,

a valve till is provided. This preferably comprises a cylindrical plug-type of valve body slidably bearinged in a bushing 61 secured concentrically in the control chamber 54 in the area thereof through which the ports 58 and 59 communicate with the control chamber. A reduced diameter port 62 through the bushing 6| registers with the bore port 58 and a reduced diameter port 63 through the bushing registers with the port 59.

The ofifset spacing between the ports 62 and B3 is preferably slightly greater than the width of an annular groove fi l formed in an intermediate portion of the periphery of the valve member lit and adapted. in one longitudinal position of the valve member to register with the port 63 and in another longitudinal position to register with the port 52. Communication between the groove 6 and a counterbore 65 in the end portion of the valve member ii exposed to low pressure Within the control chamber 54 and extending short of the roove lid is provided by a plurality of longitudinally extending communication bores 6?.

The valve member to is normally biased to assume a longitudinal position wherein the groove 84 registers with the port 63 leading by way of the port 59 to the pressure area M. This effected by means such as a coil compression spring t8 bearing against the low pressure end of the valve member 6% to drive the same normaliy to the right, as seen in Figure 4, until a radially projecting stop flange 69 on the engaged end of the valve member bears against the ad jacent end of the bushing it! which for this purpose has a Wall thickness to project into the path of the stop flange 69 clear of the adjacent wall of the control chamber The outer end of the spring bears against a plug it which closes the low pressure end of the control chamber 54 fluid tight and which has a stop pin or stem H projectin therefrom axially through the control chamber 56 to a blunt tapered tip 121 serving as a limit stop upon movement of the valve plug 63 to a predetermined limited distance in opposition to the biasing sprin to the position wherein the annular communication groove 65 in the valve plug registers with the port 62 in the valve bushing.

It will thus be apparent that in the absence of count-enforce, the spring 68 will maintain the valve member 69 in the position wherein a passage is afforded between the low pressure side of the control chamber M the port 59 by way of the counterbore the communication bores El, the communication groove and the port 63, while at the same time the valve member Gil fully blocks the port 52. Thus, at the start of operation, the pressure area Q3 is entirely out off by the valve 53 from the low pressure side of the pump; and the pressure area fi l is blocked from communication with the low pressure side of the pump by the blocking pad 39a coverin the port as a result of the modulator biasing effect of the springs 56. Hence, the full initial pumping effect of the rotor i? is directed for quick response to the outlet 32 Without any unnecessary fluid bleed-off.. If before the predetermined operating pressure is reached force tends to shift the modulator from its initial position of maximum eccentricity relative to the rotor H, the bleed-ofi port 59 is uncovered and the resulting pressure reduction in the chamber 64 effects a dynamic unbalance that assures virtually full eccentricity or" the modulator 38 until substantially the rated pressure of the pump is attained.

The valve biasing spring 68 is selected to afford, following a predetermined degree of initial compression, resistance to compression equal to the predetermined pressure rating of the pump. That is, the spring 88 is designed to hold the valve member GP: in its spring biased limit position with a pressure load which is slightly less than .the predetermined operating pressure for which the pump is rated; but after relatively slight predetermined movement of the valve body it in op position to the spring, loading thereof stiffens it to attain the desired force or pressure balance. Such movement carries the communication groove 54 in the valve body intermediate and out of communication with the ports 62 and 83 so that solid areas of the valve member 6i} will block both of the ports #22 and 63 and substantially equal dynamic modulator holding pressure will prevail in the pressure areas 43 and M.

Thrust in opposition to the spring 63 is auto- .matically effected by subjecting the head of the valve member so to dynamic pressure from the high pressure side of the pump. Hence, as the pressure fluctuates, the valve member Fit will respend and by selective exposure or communication of the pressure areas and cc to or with the low pressure side of the pump effect adjustment of the modulator block 33 to control pump displacement and maintain the desired mean pumping pressure.

Continuous exposure of the lead end of the valve mom er til to the high pressure side of the pump is effected by way of a groove l3 formed in that face of the modulator block 33 which opposes the distributor plate 52 and communicating at one end with a branch is from the high pres sure outlet port 25. This communication is constant throughout the full range of reciprocal adjustment of the modulator 33. At its opposite end the communication groove 73 has a port 75 opening into the control chamber E l in front of the valve member 56.

For a quick review of the operation of the pump and the displacement control means, reference may be had to the schematic illustration in Figure 8. The relationship of parts shown is as found in the non-operating condition of the motor unit. In this condition, the pressure areas 43 and M are in equal communication with the high pressure side of the pump but are isolated from the low pressure side of the pump until the rotor ll accelerates and the modulator 38 shifts enough to open the bleed-off port 59 whereby the pressure area ts is relieved by way of the passage afforded by the port 59, the peripheral groove t l and the passageway $1 in the valve member 50 to the rear or biased end of the valve member past the biasing spring 68 and by way of the passageway 52, 53 to the low pressure side of the pump at the inlet port i'l. As a result, the modulator 38 maintains initially maximum eccentricity of the pump chamber 4B relative to the pump rotor while the predetermined rated pressure of the pump is quickly attained. This pressure becomes active through the passageway rated, the excess pressure, reflected through the sure. foamy fluid is handled by the pump with substanpassageway 13, 14 upon the head of the valve member 60 causes the same to move further in opposition to the spring 68 and open bleed-01f communication between the pressure area 43 and the low pressure side of the pump by way of the passageway 55, 57, the port 62 and the valve groove 64 and port B? through the rear or suction end of the control chamber 54 and the passageway 52, 53. As a result the modulator block 38 is caused to shift slidably and reduce the pump displacement, thereby reducing the pump pressure. Promptly upon adjustment to the desired pressure, the valve member 55, under the influence of the biasing spring 63, returns to the neutral position wherein the communication groove 54 of the valve member is disposed between and out of communication with the ports 62 and 63. Thus, throughout the operation of the pump any fluctuations that may occur, for

example, by speed up of the rotor, variations in fluid supply or demand, and the like, are promptly reflected in automatic adjustment of the valve member SE} to control the pressure areas 43 and c4 and appropriately adjust the modulator block reciprocably.

However, by reason of the space interval between the control ports 82 and 63, tendency of the control means to hunt in response to relatively inconsequential fluctuations in pressure is minimized, This eliminates tendency of the pump to chatter or vibrate and assures positive, smooth and uniform control thereof for consequential fluctuations in pressure. While the ports 62 and 63 are blocked, of course, efficient dynamic hydraulic pressure balance prevails in the pressure areas 43 and M to hold the modulator block 38 substantially against displacement In practice, it is preferred to have the neutral space interval between the ports 52 and 63 slightly greater than the width of the valve groove 64. When the groove 54 effects communication with either of the ports 62 or 63 there is virtually instantaneous response by whatever increment clemanded by pressure fluctuations at the high pressure side of the pump for adjustment of the modulator block 38. This assures minimum pressure rise or drop in the pumping system from the desired mean pressure.

Among the many other practical advantages in a pump equipped with a control arrangement as described, it has been found that quite substantial variations in fluid temperatures can be accommodated in the pump satisfactorily and without appreciable deviation from the mean pres- It has also been found that even highly tially the same efficiency as non-foamy liquid. Of perhaps even more importance is the fact that whereas in prior art devices the available fluid would drop off at high speed, no drop-off occurs in the present pump within an extremely wide range.

It has been found desirable at times to provide restraint upon over-rapid shifting of the modulator block. 38 for pump displacement modulation under certain conditions in operation. Accordingly, it has been desirable to provide means, as shown in Figure 7, for controlling the high pressure communication duct between the areas 43 and 5 and the high pressure side of the pump. Accordingly, a somewhat thicker distributor plate 42' is provided between the face plate 25 and the body or casing block 29 to provide adequate accommodations for appropriate check valves such as ball valves ll in ports 18 between the ends of a pressure duct I9 and the respective pressure areas 43 and 44. The pressure duct I9, of course, replaces the groove duct M of Figures 1 to 6 and communicates with a pressure outlet port 8i) through the distributor plate 42' and communicating with the undercut passageway 34 for the outlet 32 in the face plate 25. Through this arrangement, sudden pressure drops in either of the pressure areas 43 or M, with a corresponding pressure surge in the remaining pressure area, and which might tend to cause back pressure in the suddenly relieved pressure area venting through the associated arm of the pressure duct I9, will be restrained by the appropriate check valve 11. Thereby jerkiness or hammering in the modulator block control circuits is avoided and smooth, quiet, efficient adjustment of the modulator block is assured.

In Figures 9 and 10 is shown a modified form of pump 86 which in functional respects is the same as the pump it already described, but in which the physical arrangement is somewhat different to have the. control valve structure in the pump housing instead of carried by the modu lator block. To this end, the pump unit 86 comprises a hollow body block 8 5 having a face plate 82 on one side and a face plate 53 on the other side with a distributor plate 84 interposed between the face plate 83 and the bodybl'ock 81,

the stacked assembly being secured together as by means such as screws 35. Except for slightly different edge contour, the face. plate 83 is the same as the previously described face plate 25 and has appropriate fluid inlet and outlet passages which communicate with semi-circular kidney shape inlet and outlet ports 87 and 88, respectively, in the distributor plate 84. A straight walled chamber 89 within the body block SI has a modulator block 90 rectilinearly slidably mounted therein and affords pressure areas 9| and 92, respectively, at the oppositeends of the modulator block. A circular pump chamber 93 in the modulator block. normally ,eccentrically encircles a. rotor 96 driven by a shaft 95 and having radially slidable vanestt just. like the rotor ll of the pump unit Iii. A priming spring 91 acts in the non-operating condition of the pump to urge the modulator block 9t toward eccentric relation relative to the rotor M so as to assure that in starting the pump the modulator block will not be in a position of neutrality or zero fluid displacement. Communication between the pressure areas SI and 92 and the high pressure side of the pump is eflected through the medium of appropriate respective communication ducts 98 and 99 in the modulator block opposing face of the distributor plate 84 and leading from the outlet port 88 therein.

Reciprocal adjustment of the modulator block 90 is effected in substantially the same manner as in the pump unit I5 except that a control valve I operatively mounted in a control chamber ml in the body block 8I at one side of the modulator block chamber 89 is utilized. Low pressure or suction communication between the pump and one end of the control chamber In! is efiected by way of a passage I02 that is formed in the distributor plate Bil and which communicates by way of a port I83 with the control chamber. High pressure communication between the opposite end of the control chamber IOI and the high pressure side of the pump is effected by way of a port I04 in the body blocl: which communicates with an arm I leading from the discharge port 88 in thedistributor plate.

The control valve I00 is in all essential respects the same as the control valve 60 of the pump unit It and comprises a cylindrical body, a solid end of which is exposed to high pressure in the control chamber WI and the opposite end of which is engaged by a biasing spring I01 of predetermined load and against the force of which the valve member I00 is driven by high pressure exerted against the high pressure end thereof.

Upon attainment of the predetermined pressure in the high pressure end of the control chamber 10!, the valve member ltd is driven a prede termined distance in opposition to the biasing spring I0? until a peripheral groove !98 in the valve member shifts out of registry with a port I09 which communicates by way of a passage I :0

in the distributor plate 84 with the pressure area 0! and by which communication is selectively effected with the low pressure side of the pump. At the mean pressure, the valve groove Itt isdisposed intermediate the port It and a low pres sure communication port III, which communi cates by way of a passage H2 in the face plate 82. with the pressure area 92. Limit upon shifting of the valve member I00 in opposition to the spring I0! is efiected by a stop pin I I3, which serves to hold the valve member we against movement beyond registration of the groove I08 with the port iII in the maximum rearward shifting of the valve member.

Operation of the modified pump unit 86 is substantially the samev as operation of the pump unit I5. In the non-operating position of the pump unit, the modulator block is in its posi tion of maximum eccentricity relative to the rotor 9 under the influence of the priming spring 97?. As soon as the pressure is built up within the pump after starting thereof, the influence of the high pressure in the forward end of the control chamber IOI, acts upon the valve member E00 and when the rated mean pressure is attained, the valve member I00 is shifted to the neutral position wherein both of the pressure areas SH and 92 are isolated and maintained in substantially dynamic fluid pressure balance to hold the modulator 90 against displacement.

Upon increase in the pump pressure beyond the rated mean pressure, immediate reaction of the valve member I00 causes it to move further against the spring I01 and ei fect communication of the pressure area 92 with the low pressure or suction side of the pump by way of the port I I I and as a result the modulator as is shifted to reduce the pump displacement and the pressure promptly returns to the predetermined mean pressure output of the pump and the valve member I00 slides back to its neutral position wherein the modulator 90 is held substantially against displacement by the dynamic pressure fluid balance in the pressure areas iii and 32. Should the pressure drop, the valve member iil il moves to effect registration of the groove 56-3 with the port I09 and the modulator iii] shifts to increase the fluid displacement of the pump. This process continues automatically as long as the pump is in operation. The mean pressure for which the pump is rated is thus maintained smoothly and continuously.

Should the fluid demand cease abruptly, the valve member I 00 can respond instantly to move to its limit against the pin H3 and thus cause the modulator 90 to shift to its concentric limit relative to the rotor 94 to relieve any tendency to overload the pump. Then as the pump continues in operation only such limited displacement will prevail automatically as will maintain the rated pressure until there is again a fluid demand and the pump responds with unusually small initial pressure drop.

The modification shown schematically in Figures ll, 12 and 13, depicts a control arrangement that is applicable as an alternative for the control arrangement disclosed in connection with either of the pump units l or 86. The principal difference resides in the control of high pressure fluid to the pressure areas at opposite sides of the modulator block by the control valve. This may be eiiected in addition to the direct communication of the pressure areas with the high pressure side of the pump or as an alternative to such direct communication. Accordingly, main pump body block B has modulator block M slidable therein and with pressure areas P and P at the opposite ends of the modulator block. Where direct communication of the pressure areas with the pump chamber is desired, the pressure areas may be maintained in somewhat restricted though constant high pressure communication with the high pressure side of the pump by passageway or duct D, corresponding substantially to the previously described duct ll in Figure 3. As an alternative, or in addition, a duct DD may be provided which afiords restricted direct communication between the pressure area chambers P and P Valve unit V comprises a reciprocable plug type valve body H5 having a pair of axially spaced peripheral grooves Ill and H8 and is normally biased to one limit position by a spring H9. In this position of the valve body H5, high pressure fluid is conducted by way of a duct 120 from discharge port HP to the front end of control chamber l2l whence the high pressure fluid passes through the adjacent end of the valve body I 55 through a duct I22 and by way of the groove H7 into a branch I23 of a high pressure fluid duct I24 that leads to the pressure area P In the initial or starting condition of the pump, a bleed-off duct lit for effecting communication between the pressure area P and the groove H8 in the valve member H5 is blocked by means such as an end spacer portion l26 on the modulator M. From the groove H8 leads a passage 121 through the rear end of the valve member H5 for communication past the spring H9 and through a duct 23 with the low pressure side of the pump at the inlet or low pressure port LP. Any tendency toward reduction in displacement of the pump before attaining rated pressure is controlled by opening of the bleed-off duct I25.

As the pressure mounts toward the rated pressure of the pump, which is predetermined by the load capacity of the spring H9, the valve member H5 is shifted by spring-compressing thrust of the highv pressure fluid on the end thereof opposite the spring H9 until the grooves H1 and H3 are displaced to cut-01f position relative to the openings to the ducts H3 and I25. In this condition, the modulator block M is held substantially in dynamic pressure balance against displacement, as shown in Figure 12.

Should the pressure increase beyond the predetermined mean pressure rating of the pump, the valve member H5 is shifted by force of the high pressure fluid on the end thereof opposite to the spring H9 and the spring yields until the condition shown in Figure 13 is attained wherein the high pressure groove H'l moves toward or into registration with a duct branch I29 of the duct I25 so that high pressure fluid passes to the pressure area P At the same time the groove H8 moves toward or into registration with a duct branch l30 of the duct I24 and thus opens the pressure area P to the low pressure or suction side of the pump, shifting the modulator M to the extent required to modify the pump displacement and return the pressure to the rated mean. Thus, the valve member H5 will shift reciprocably from the neutral position of Figure 12 toward and into the positions of Figures 11 and 13 as demanded by tendency toward pressure fluctuations whereby to shift the modulator M selectively for controlling the pump displacement for maintaining the constant mean pressure desired.

Throughout the operation of the pump, fluid from the high pressure side of the pump is delivered equally by passageway D to the pressure areas or chambers P and P and/or the duct DD affords direct pressure communication between the chambers, so that in a sense both chambers are at all times pressure primed. As a result, operation of the valve controlled pump modifyin system is rendered more quickly responsive, especially in rapid changes in volume demands upon the pump.

In order to assure that the modulator block M will not remain in neutral position when the pump is stopped, a priming spring [3| is preferably in erposed between the end of the block and the opposing wall of the pressure area P such spring herein comprising a leaf spring, although a coiled compression spring as in Figures 3 and 9 u could be substituted.

The manner in which the control arrangement of Figure 11 may be adapted to the pumpslE and 3% will be readily apparent. Whether the pressure passages or ducts D and DD will be used at all, or used separately, or together, will substantially depend in any specific pump unit upon numerous factors, including the size, weight or proportions of the various elements of the pump.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention, and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

We claim as our invention:

1. In a constant pressure variable displacement pump, means defining a modulator chamber, a modulator movable therein and defining with the walls defining the chamber fluid subchambers separated by the modulator, the modu lator having a circular pump chamber therein, a rotary impeller on a fixed axis operating in said pump chamber and having impelling means cooperative with the annular wall defining the pump chamber to vary the pump displacement as the modulator moves in said first mentioned chamber, low pressure and high pressure ports respectively communicating with low pressure and high pressure sides of the pump chamber, a'

against the opposite end of said valve and normally biasing the valve to resist movement of the valve responsive to the pump pressure with predetermined force, a fluid passagecommunicating with the low pressure side of the pump, and respective fluid passages communicating with said subchambers, said plunger valve controlling said low pressure and said sub-chamber fluid passages and in its maximum spring biased position effecting communication between the low pressure fluid passage and the passage from one of said subchambers to assure displacement of the modulater into said sub-chamber, the valve being movable by pump-created pressure in excess of the spring bias to efiect communication between the fluid passage from said one sub-chamber and the high pressure fluid passage from the pump and coincidentally'effect communication between the low pressure passage and the passage from the remaining sub-chamber whereby to cause shifting of the modulator toward or into said remaining sub-chamber.

2. In a constant pressure variable displacement pump, means defining a modulator chamber, a modulator movable therein and defining with the walls defining the chamber fluid sub-chambers separated by the modulator, the modulator having a circular pump chamber therein, a rotary impeller on a fixed axis operating in said pump chamber and having impelling means cooperative with the annular wall defining the pump chamber to vary the pump displacement as the modulator moves in said first mentioned chamber, low pressure and high pressure ports respectively communicating with low pressure and high pres sure sides of the pump chamber, a reciprocable plunger valve, 2. fluid passage communicating with the head of the valve and with the high pressure side of the pump chamber and normally exposing the head of the valve to pressure created by the pump, a spring operating against the opposite end of said valve and normally biasing the valve to resist movement of the valve,

responsive to the pump pressure with predetermined force, a fluid passage communicating with the low pressure side of the-pump, and respectiv fluid passages communicating with said subchambers, said plunger valve controlling said low pressure and said sub-chamber fluid assages and in its maximum spring biased position effecting communication between the low pressure fluid passage and the passage from one of said subchambers to assure displacement of the modulator into said one sub-chamber, the valve being movable by pump-created pressure in excess of the spring bias to eiTect communication between the fluid passage from said one sub-chamber and the high pressure fluid passage from the pump and coincidentally effect communication between the low pressure passage and the passage from the remaining sub-chamber whereby to cause shifting of the modulator toward or into said remaining sub-chamber, said valve being carried entirely by the'modulator and all of said fluid passages being in said modulator.

3. In a constant pressure variable displacement pump, means defining a modulator chamber, a modulator movable therein and defining with the walls defining the chamber fluid sub-chambers separated by the modulator, the modulator hav ing a circular pump chamber therein, a rotary impeller on a fixed axis operating in said pump chamber and having impelling means cooperative with the annular wall defining the pump chamber to vary the pump displacement as the modulator moves in said first mentioned chamber, low pressure and high pressure ports respectively communicating with low pressure and high pressure sides of the pump chamber, a reciprocable plunger valve, a fluid passage communicating 14 with the head of the valve and with the high pressure side of the pump chamber and normally exposing the head of the valve to pressure created by the pump, a spring operating against the opposite end of said valve and normally biasing W the valve to resist movement of the valve relator into said one sub-chamber, the valve being movable by pump-created pressure in excess of the spring bias to effect communicationbetween the fluid passage from said one sub-chamber and the high pressure fluid passage from the pump and coincidentally efiect communication between the low pressure passage and the passage from the remaining sub-chamber whereby to cause shifting of the modulator toward or into said remaining sub-chamber, said valve being carried bysaid means defining the modulator chamber and said fluid passages also being in said means.

4. In combination in a constant pressure variable displacement pump, means defining a casing having a modulator chamber therein, a modulator member in said chamber and dividing the chamber into fluid areas at opposite sides of the modulator and into which areas the modulator is alternately movable, the modulator having a circular pump chamber therein, a pump rotor operable on a fixed axis in said pump chamber and having means cooperating with the wall defining the pump chamber for variable fluid displacement, the wall of the casing opposing one face of the modulator having a, duct therein communicating with the high pressure side of the pump chamber and having ports at its opposite ends communicating with the respective fluid areas, and respective check valves at said ports permitting flow of fluid from the pressure side of the pump into said areas but blocking return flow of fluid.

5. In combination in a constant pressure variable displacement pump construction, means defining a modulator chamber, a modulator movable in said chamber and cooperating with the walls, of the chamber to define fluid pressure areas at opposite sides of the modulator into which the modulator is movable, the modulator having a circular pump chamber therein, a fixed axis rotor in said pump chamber having means cooperating with the annular wall defining the pump chamber to efiect variable fluid displacement as modified by the modulator moving in said modulator chamber, fluid passages extending from the respective fluid pressure areas, a fluid passage extending from the high pressure side of the pump, a fluid passage extending to:

a low pressure source, means defining a. valve chamber, a valve member movable in said chamher, all of said passages communicating with said valve chamber, and means acting against one side of the valve member to bias the valve member normally in one direction, the fluid passage:

from the high pressure side of the pump communicating with the opposite side of the valve member and normally acting to move it in opposition to said biasing means, passages in said valve member affording communication selectively between said low and high pressure passages and said pressure area passages and being arranged to effect communication between the high pressure passage and one of said pressure area passages in the fully biased position of the valve member while at the same time effecting communication between the low pressure passage and the remaining pressure area passage, and alternating the connection between the respective pressure area passages and the low and high pressure passages when the valve member is moved in opposition to said biasing means by pump created pressure.

6. In combination in a variable displacement pump including a housing having therein a modulator chamber, a modulator member having a pump chamber therein and being narrower than said modulator chamber on one transverse axis through said chamber, means on the modulator and on the housing within said modulator chamber and disposed on an axis transverse to said first mentioned axis and cooperating to provide a substantial pressure fluid seal between the modulator and the housing to divide the areas of the modulator chamber through which said first mentioned axis extends into subchambers to which respective opposite peripheral areas of the modulator are directly exposed, a fixed axis pump rotor in said pump chamber and having means cooperating with the wall defining said pump chamber to effect variable fluid displacement as modified by the modulator movable in said modulator chamber, means defining a restricted pressure bleed passage between the high pressure side of the pump and each of said subchambers, and control means providing a pressure passage communicating with the high pressure side of the pump chamber and respective separate passages communicating with said sub-chambers, a low pressure passage, said control means also providing a valve chamber with which all of said passages communicate, a valve member in said valve chamber and responsive to pump created pressure delivered thereto by said pressure passage for controlling said separate passages for subjecting said sub-chambers automatically and selectively to said low pressure passage for determining the relation of the modulator to said pump rotor and thereby determining displacement of the pump.

7. A variable displacement pump as defined in claim 6, including in addition means in said one sub-chamber normally biasing the modulator into maximum displacement relation to the pump rotor in order to assure full pump displacement at the beginning of operation.

8. In combination in a variable displacement pump construction, means defining a modulator chamber, a modulator operable shiftably in said chamber and defining in said chamber opposite sub-chambers to which opposite peripheral surfaces of the modulator are constantly exposed, the modulator having a pump chamber therein, a fixed axis pump rotor operable in said pump chamber and having means cooperable in fluid displacement relation with the wall defining said pump chamber, the modulator being movable in said modulator chamber relative to said rotor to determine the pump displacement, means Within the confines of said modulatorchamber-defining means including a valve chamber and passages communicating between said valve chamber and said sub-chambers and said pump chamber, and a valve in said valve chamber having means affording communication se lectively between said pump chamber and said passages communicating with the sub-chambers, said valve being operative automatically in response to pump created pressures communicated thereto by said passage communicating with the pump chamber whereby to vary the position of the valve relative to said passages communicating with the sub-chambers to control the communication of said communication means with these passages and thereby to control the position of the modulator relative to the pump rotor by subjecting the exposed areas of the modulator periphery within said sub-chambers to variable pump pressures, and restricted flow area pressure bleed passage means effecting communication between the high pressure portion of the pump chamber and at least one of said subchambers in addition to and independent of said control means.

9. In combination in a constant pressure variable displacement pump, means defining a casing having a modulator chamber therein, a modulator member in said chamber and dividing the chamber into fluid areas at opposite sides of the modulator and into which areas the modulator is alternately movable, the modulator having a circular pump chamber therein, a pump rotor operable on a fixed axis in said pump chamber and having means cooperating with the wall defining the pump chamber ior variable fluid displacement, the wall of the casing opposing one face of the modulator having a bleed duct therein communicating with the high pressure side of the pump chamber and having its opposite end portions communicating with the respective fluid areas for subjecting said areas to dynamic balance of pump pressure during operation, and means for'establishing communication between a low pressure source and any one of said fluid areas selectively to effect a pressure unbalance between the fluid areas to thus shift the modulator for varying the fluid displacement of the pump.

10. In combination in a constant pressure variable displacement pump, a housing structure defining a modulator chamber, a modulator structure adjustably movable in said chamber, the modulator structure having oppositely directed surface portions cooperative with portions of said housing structure to define respective fluid pressure sub-chambers into and out of which said surface portions are alternately selectively movable responsive to pressure difierentials in said sub-chambers for thereby adjustably moving the modulator structure, said modulator structure having a pump chamber therein, a rotor mounted on a fixed axis with respect to said housing structure and operable in said pump chamber, said rotor having means cooperating With the wall defining the pump chamber to. effect variable fluid displacement as modified by the modulator structure as adjustably positioned in said modulator chamber, said housing structure providing fluid supply and fluid discharge ports communicating respectively with the low and high pressure side of said pump chamber, one of said structures providing a valve chamber, a valve movably mounted in said valve chamber, a fluid passage connecting the high pressure side of the pump chamber with said valve chamber in such relation to said valve as to impress upon the valve pump-created high pressure to move the valve automatically in one direction during op eration of the pump, means normally biasing the valve in the opposite direction in opposition to the 17 pump pressure impressed thereon, a low pressure exhaust passage leading from said valve chamber, respective communication passages connecting said sub-chambers with said valve chamber, said valve being operable to efiect communication with one of said communication passages and said exhaust passage in the maximum biased position of the valve efiected by said hiasing means, said valve being movable in said one direction by pump pressure in excess of a predetermined biasing value of said biasing means to close said one communication passage and open the other communication passage to said exhaust passage, while during pump created pressure substantially balancing said predetermined value of the biasing means the valve assumes a position blocking communication between both of said communicating passages and said exhaust passage, and passage means connecting the high pressure side of the pump chamber and said sub-chambers for pressure priming said sub-chambers and also for maintaining said sub-chambers in substantially pressure balanced relation in the positions of the valve wherein both of said communicating passages are blocked from said exhaust passage, said valve reacting automatically to dynamic pressure variations from a mean pump pressure determined by the predetermined biasing force of said biasing means for controlling the pressure in said sub-chambers by controlling said communicating passages with respect to said exhaust passage as aforesaid.

11. A combination as defined in claim 10, wherein the passage means connecting the sub-chambers and the high pressure side of the pump 18 chamber comprises a duct independent of said valve chamber.

12. A combination as defined in claim 10, wherein the passage means connecting the high pressure side of the pump chamber and said sub-chambers comprises a high pressure passage leading from the valve chamber and controlled by the valve and communicating with one of said sub-chambers and a further passage connects the sub-chambers together for high pressure balance.

13. A combination as defined in claim 10, wherein the passage means connecting the high pressure side of the pump chamber with said sub-chambers comprises respective high pressure ducts under the control of said valve and leading from said valve chamber to said subchambers respectively.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,943,929 Rayburn Jan. 15, 1934 2,062,310 Hittell Dec. 1, 1936 2,238,061 Kendrick Apr. 15, 1941 2,238,062 Kendrick Apr. 15, 1941 2,296,876 Samiran et al Sept. 29, 1942 2,433,484 Roth Dec. 30, 1947 2,451,279 DeLancey Oct, 12, 1948 2,451,666 DeLancey Oct.. 19, 1948 FOREIGN PATENTS Number Country Date 489,955 Great Britain Aug. 5, 1938 528,950 Great Britain Nov. 11, 1940 

